The present invention relates to the preparation of dihydroxydiphenyl alkanes by the reaction of phenol and dihaloalkanes. More particularly, it relates to an improved method for preparing 4,4'-dihydroxydiphenylethane sometimes referred to as bisphenol E.
Dihydroxydiphenyl alkanes, also known as bisphenols, are useful in the production of high polymers, epoxy resins and high-molecular weight thermoplastic condensates as well as intermediates in organic syntheses, the best known of such compounds, bisphenol A, being widely employed. It has been suggested in an article by I. M. Nosalevich et al entitled "Preparation of dihydroxydiphenylalkanes by the alkylation of phenol by dihaloalkanes" [(Vestn. Khar'kov. Politekh. Inst. 1971, No. 60, 61-4) (Ukrain)] that an increase in the number of technically available dihydroxydiphenyl alkanes would open up possibilities for modification of polymeric materials formed from them. Following this line, these workers have described several methods of preparing dihydroxydiphenyl alkanes among which is that of the direct interaction of phenol with dichloroethane or dibromoethane in the presence of zinc to give the 1,2 - bis (4-hydroxyphenyl) ethane (also known as 4,4'-dihydroxydiphenylethane) and its isomers. It has now been discovered that if the reaction of phenol and a dihaloethane is conducted in the presence of iodine as a promoter with various zinc-containing catalysts, the rate of reaction is significantly increased and lower temperatures can be employed.